The present invention relates to an eye's optical characteristics measuring system for measuring ocular refractive power parameters and optical characteristics of an eye under test such as ocular refractive degree, astigmatic degree, astigmatic axis, etc.
In the past, as an ocular refractive power measuring system, there is an objective type ocular refractive power measuring system. By this system, a target image is projected to a fundus of an eye under test, and the target image reflected from the fundus of the eye under test is received by a photoelectric detector, and ocular refractive power parameters such as ocular refractive degree, astigmatic degree, astigmatic axis, etc. are measured from a received image.
In the objective type ocular refractive power measuring system as described above, when astigmatic parameters such as ocular refractive power (spherical refractive power), astigmatic degree (cylindrical refractive power), astigmatic axis, etc. are measured, a luminous flux in complete round ring form is projected to the fundus of the eye under test as the target image, and roundness (circularity) of the target image received by the photoelectric detector is detected. For instance, in case the eye under test has astigmatism, the received image is in elliptical shape. From the elliptical shape (flatness), astigmatic degree (C) can be obtained, and astigmatic axis angle A is measured from a tilt angle of the ellipse (tilt angle of longer axis of ellipse).
In the conventional type ocular refractive power measuring system, the luminous flux in ring form is projected for the measurement of ocular refractive power. As a result, a projected luminous flux and a reflected luminous flux are under influence of factors such as configuration of a cornea, an edema, turbidity of a crystalline lens, etc. Thus, there are such problems that the elliptical shape of the received image is collapsed and accurate measurement cannot be performed.
Further, in the conventional type ocular refractive power measuring system, it is not possible to objectively observe which kind of image is formed on the fundus of the eye under test.
As the ocular refractive power measuring system for measuring ocular refractive power by projecting the luminous flux in ring form, for instance, a system is shown in JP-A-1-129830.